This invention relates generally to fuel injection systems for internal combustion (diesel) engines, and more particularly to injectors that introduce the fuel into the combustion chambers of the engine. The injector disclosed herein is suitable for use with an injection system that is actuated mechanically, hydraulically, electrically, or with a hybrid of any of the foregoing.
In recent years there has been renewed interest and impetus to develop more efficient internal combustion engines that also produce lower levels of emissions or other environmentally undesirable byproducts. It has been determined that these objectives may be accomplished in part by altering the timing of fuel injection with respect to piston or crankshaft position, and by obtaining a high injection pressure, short injection duration, variable injection duration, and a sharp end of injection with no leakage or secondary injection.
Efforts to achieve these objectives with conventional camshaft driven injectors have not met all of these objectives because of the inherent restraints of a mechanical system. Most noteably, the combination of camshaft, push rods, rocker arms, etc. usually results in a rigid timing program that cannot be altered. Efforts to advance or retard injection timing have included hydraulically expandable tappets to lengthen or shorten a camshaft drive train. Such tappets have met with some success, but have not permitted alteration of the other injection parameters affecting engine performance.
As a result, manufacturers have experimented with other means to activate fuel injectors, including electrical systems, hydraulic systems, and systems that are a hybrid of both. These systems result in the application and removal of great, yet precise, amounts of force almost instantaneously, in order to achieve the desired injection characteristics yet not damage the injector itself. Thus, the diesel injector must not only inject the fuel in accordance with the aforementioned objectives, it must also withstand the instantaneous pressures applied thereto.